Cat scratch disease (CSD) is regional lymphadenopathy caused by Bartonella henselae bacteria. Painful swelling develops in lymph nodes near the inoculation site 1-3 weeks after cat (especially kitten) scratch or bite. Most commonly axillary and epitrochlear (upper extremity inoculation) or inguinal (lower extremity) lymph nodes are involved. Common in children and young adults. Necrotizing granulomatous lymphadenitis is characteristic — stellate (star-shaped) micro-abscesses are the histological diagnostic finding. Self-limiting in immunocompetent individuals, spontaneously resolving in 2-4 months. Severe complications like bacillary angiomatosis and peliosis hepatis may develop in immunosuppressed patients (HIV).
Age Range
5-25
Peak Age
12
Gender
Equal
Prevalence
Uncommon
B. henselae enters skin through cat scratch or bite and is phagocytosed by dermal macrophages. Bacteria multiply intracellularly and are carried to regional lymph nodes via lymphatic channels. Papule/pustule develops at inoculation point after 3-10 days (primary lesion). Granuloma formation begins in lymph node — epithelioid histiocytes, giant cells, and neutrophils form organized structures. Neutrophilic micro-abscesses (stellate abscesses) develop in granuloma centers — different from caseous necrosis in TB, seen as small necrotic foci on imaging. Perifocal inflammation is prominent — edema and vascular congestion in perinodal fat tissue appear as perinodal inflammatory changes on CT and US. Self-limiting course results from granulomatous response controlling bacteria.
Primary lesion (papule/pustule) at cat scratch/bite point, regional painful necrotic lymphadenopathy, and prominent perinodal inflammatory changes is the diagnostic triad of cat scratch disease.
Enlarged (usually 2-5 cm), hypoechoic or mixed echogenicity lymph node. Intranodal necrosis (anechoic foci) is common. Hilum lost or narrowed. Prominent perinodal inflammatory changes — edema, thickening, and hyperechogenicity in surrounding soft tissue. Abscess formation may develop. Usually single station, single or few nodes involved.
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Enlarged, hypoechoic lymph node with intranodal necrosis in ... region with prominent perinodal inflammatory changes — consistent with cat scratch disease in clinical context.
Increased vascularity on Doppler — hilar and perinodal vascularity increase. Avascular zones in necrotic areas. Perinodal inflammatory tissue shows prominent hyperperfusion. RI may be mildly elevated. Peripheral vascularity in abscess formation.
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Increased vascularity in lymph node and perinodal area with avascular zones in necrotic areas — consistent with inflammatory lymphadenopathy.
Enhancing lymph node (homogeneous or rim type) on contrast-enhanced CT. Prominent perinodal inflammatory changes — fat stranding, soft tissue thickening. Central necrosis foci may be seen. Usually single station, 1-3 nodes involved. If abscess formation has developed, peripherally enhancing low-density collection.
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Enhancing lymph node in ... region with prominent perinodal fat stranding and soft tissue thickening — consistent with inflammatory/granulomatous lymphadenopathy.
Diffusion restriction on DWI — granulomatous tissue shows low ADC. Heterogeneous ADC in necrotic foci. Heterogeneous high signal on T2 (inflammation + necrosis). Post-contrast enhancement and perinodal inflammatory enhancement is prominent.
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Diffusion restriction and heterogeneous signal in necrotic foci on DWI in lymph node — consistent with granulomatous lymphadenopathy.
Focal moderate FDG uptake on PET-CT (SUVmax usually 3-8). Single station involvement is characteristic. Perinodal inflammatory tissue may also take up FDG. May mimic lymphoma — clinical context (cat contact, age, acute presentation) and single station involvement are distinguishing.
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Focal FDG uptake (SUVmax: ...) in lymph node at ... region — cat scratch disease should be considered in clinical context.
Criteria
Self-limiting regional LAP, immunocompetent individual, spontaneous regression in 2-4 months.
Distinct Features
Single station LAP, necrosis and perinodal changes prominent. Antibiotics usually not needed. Drainage if aspiratable abscess forms.
Criteria
In HIV or immunosuppressed patients. Bacillary angiomatosis, peliosis hepatis, bacteremia, endocarditis may develop.
Distinct Features
Widespread LAP, hepatosplenomegaly, skin lesions (bacillary angiomatosis). Multiple small hypodense lesions in liver/spleen on CT (peliosis). Antibiotic treatment mandatory.
Criteria
Conjunctival inoculation + ipsilateral preauricular LAP. 5% of patients.
Distinct Features
Unilateral conjunctivitis + preauricular LAP. Self-limiting. Necrotic preauricular node on US.
Distinguishing Feature
TB shows matting, multi-region involvement, chronic course, and calcification — CSD shows single station, acute presentation, prominent perinodal changes, and less matting.
Distinguishing Feature
NHL shows multiple station involvement, conglomerate LAP, intense FDG uptake — CSD shows single station, acute painful LAP, moderate FDG, and cat contact history.
Distinguishing Feature
SCC metastasis shows painless node, known primary tumor, ENE, and less perinodal changes — CSD shows tender node, cat contact, prominent perinodal inflammation, and self-limiting course.
Distinguishing Feature
Kikuchi shows young female, cervical LAP, necrosis may be present but perinodal changes not as prominent as CSD, and no cat contact.
Urgency
routineManagement
conservativeBiopsy
Not NeededFollow-up
3-monthCSD in typical presentation (cat contact + regional painful LAP + young age) can be managed with clinical diagnosis — biopsy usually not needed. Serological tests (B. henselae IgM/IgG) support diagnosis. Self-limiting in immunocompetent individuals — antibiotics usually not needed. Aspiration/drainage for large abscess formation. In atypical presentation (immunosuppression, multi-organ involvement), biopsy and antibiotics (azithromycin) required. Follow-up US at 3 months to assess regression.
Cat scratch disease is usually self-limiting in immunocompetent patients (resolves in 2-4 months). Azithromycin treatment may be given in symptomatic cases. Bacillary angiomatosis and peliosis hepatis may develop in immunosuppressed patients (HIV) — aggressive antibiotic treatment is required in this situation. Hepatosplenic micro-abscesses (target lesions) are characteristic in disseminated form. Diagnosis is confirmed by Bartonella serology.